Bump eslint from 4.19.1 to 6.7.2

Bumps [eslint](https://github.com/eslint/eslint) from 4.19.1 to 6.7.2.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v4.19.1...v6.7.2)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -27,7 +27,7 @@
   },
   "devDependencies": {
     "chai": "^3.5.0",
-    "eslint": "^4.18.2",
+    "eslint": "^6.7.2",
     "mocha": "^2.4.5",
     "mock-fs": "^3.9.0",
     "sinon": "^1.17.4"